I missed it :-)

> On Jul 22, 2016, at 3:53 PM, 'Norman Maurer' via Netty discussions 
> <[email protected]> wrote:
> 
> Isn’t this what I did ?
> 
> https://github.com/netty/netty/pull/5569/files#diff-23eafd00fcd66829f8cce343b26c236aR238
>  
> <https://github.com/netty/netty/pull/5569/files#diff-23eafd00fcd66829f8cce343b26c236aR238>
> 
> 
>> On 22 Jul 2016, at 15:52, [email protected] 
>> <mailto:[email protected]> wrote:
>> 
>> perhaps you should add a comment saying that no reference to Stack objects 
>> should be kept.
>> 
>> Le vendredi 22 juillet 2016 12:04:26 UTC+2, Norman Maurer a écrit :
>> Could you test : 
>> 
>> https://github.com/netty/netty/pull/5569 
>> <https://github.com/netty/netty/pull/5569> 
>> 
>> ? 
>> 
>> > Am 22.07.2016 um 11:58 schrieb Julien Viet <[email protected] 
>> > <javascript:>>: 
>> > 
>> > Yes with branch netty-4.1.3.Final 
>> > 
>> >> Le 22 Jul 2016 à 09:21, 'Norman Maurer' via Netty discussions 
>> >> <[email protected] <javascript:>> a écrit : 
>> >> 
>> >> Yes this sounds not right… So what are the steps to reproduce ? Fire up a 
>> >> vm, checkout vert.x master and run the build ? 
>> >> 
>> >> 
>> >>> On 22 Jul 2016, at 00:51, Julien Viet <[email protected] 
>> >>> <javascript:>> wrote: 
>> >>> 
>> >>> Hi, 
>> >>> 
>> >>> we are seing OOM "GC overhead limit exceeded"  issue in Vert.x test 
>> >>> suite on slow machines like Cloudbees or using virtualization on a 
>> >>> laptop. 
>> >>> 
>> >>> This issue means that the VM spend more time in GC than the rest of the 
>> >>> VM (98%), but I’m pretty sure everyone here knows that already. 
>> >>> 
>> >>> In the case of Vert.x testsuite, it happens because we create and 
>> >>> destroy many Vertx instances and therefore many event loops / threads 
>> >>> during the tests. 
>> >>> 
>> >>> I spent quite some time on the issue and I found that it happens because 
>> >>> the ThreadDeatchWatcher's Recycler DELAYED_RECYCLE fast thread local is 
>> >>> a WeakHashMap<Stack, WeakOrderQueue) used by the ThreadPoolCache grows 
>> >>> and retains many entries (up to 2000). This WeakHashMap contains 
>> >>> recycled objects with large footprint and also the Stack itself 
>> >>> reference its Thread that has a large footprint. 
>> >>> 
>> >>> I am not saying it is a leak per se, but the maps grows and takes time 
>> >>> to be garbaged. This does not prevent the testsuite to run on a laptop 
>> >>> but it slows it down and on a slow machines it prevents running the 
>> >>> testsuite entirely. 
>> >>> 
>> >>> I believe this behavior was introduced by this commit : 
>> >>> https://github.com/netty/netty/commit/afafadd3d7caf1e4b346da049baab0afeae0a4bc
>> >>>  
>> >>> <https://github.com/netty/netty/commit/afafadd3d7caf1e4b346da049baab0afeae0a4bc>
>> >>>  
>> >>> 
>> >>> The change that makes the whole difference is : 
>> >>> https://github.com/netty/netty/commit/afafadd3d7caf1e4b346da049baab0afeae0a4bc#diff-23eafd00fcd66829f8cce343b26c236aR226
>> >>>  
>> >>> <https://github.com/netty/netty/commit/afafadd3d7caf1e4b346da049baab0afeae0a4bc#diff-23eafd00fcd66829f8cce343b26c236aR226>
>> >>>  
>> >>> 
>> >>> The introduction of the field stack in the WeakOrderQueue keeps a 
>> >>> reference on the Stack objects, however Stack instances are also weak 
>> >>> keys of the fast thread local WeakHashMap and therefore defeats the 
>> >>> purpose of the WeakHashMap. Not entirely as it is GC’ed but much less 
>> >>> often and increase the memory footprint. 
>> >>> 
>> >>> let me know what you think 
>> >>> 
>> >>> Julien 
>> >>> 
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